Furthemore, the pan-caspase inhibitor zVAD-fmk significantly suppressed the synergistic cytotoxicity induced by co-treatment with SSa or SSd and cisplatin BB-94 (Figure 2E and 2F). Collectively, these results suggest that apoptosis is involved in the potentiation of cytotoxicity caused by saikosaponins and cisplatin co-treatment. Figure 2 Saikosaponins and cisplatin co-treatment potentiates apoptosis in cancer cells. (A) HeLa cells were treated with cisplatin (8 μM) or saikosaponin-a

(10 μM) or saikosaponin-d (2 μM) individually or combination of saikosaponin and cisplatin for 36 h and then stained with ethidium bromide and acridine orange; Cells were immediately observed and photographed under a fluorescence microscope. (B) HeLa cells were treated as indicated in (A), and then stained with annexin V and PI followed by flow cytometry analysis. Early apoptosis is defined by Annexin V+/PI- staining (Q4) and late apoptosis is defined by Annexin V+/PI+ staining (Q2). (C) and (D) HeLa cells were treated with cisplatin (8 μM) or saikosaponin-a (10 μM) or saikosaponin-d (2 μM) individually or combination of saikosaponin and cisplatin for 24 h and 36

h. Caspase -3 and PARP were detected by western blot. β-actin was detected as an input control. (E) and (F) HeLa cells were pretreated with zVAD-fmk (20 μM) for 30 min or remained untreated and then treated with saikosaponin-a Selleck Necrostatin-1 or -d and cisplatin for another 48 h. Cell death was measured as described in Fig. 1A. Saikosaponins induce intracellular ROS accumulation in cancer cells ROS such as superoxide anion (.O2 -) and its reduced product hydrogen peroxide (H2O2) have been considered as cytotoxic byproducts of cellular metabolism, and the accumulation of ROS in cells may promote cell death. Although saikosaponins have been reported to be antioxidants that improve hepatic antioxidant Thiamet G capacity and protects against CCl4-induced liver injury in rats [24], their roles in intracellular

redox modulation have never been addressed. To investigate the mechanism of the saikosaponins and cisplatin-induced cytotoxicity, we examined the effect of saikosaponin and cisplatin on ROS levels in HeLa cells. Cells treated with saikosaponin, cisplatin, or both were stained with two ROS-specific dyes, CM-H2DCFDA that is specific for hydrogen peroxide (H2O2) or DHE that is specific for.O2 -. Cisplatin had marginal effect on cellular.O2 – level. Whereas, either SSa or SSd PRI-724 strongly induced cellular.O2 – accumulation (Figure 3A, rightward shift of the peaks). The treatment with SSa or SSd plus cisplatin retained similar trend of.O2 – induction as treated by the saikosaponins alone. Similar trend and more striking extent of H2O2 induction by SSa or SSd, alone or in combination with cisplatin were observed (Figure 3B).